The Tarwin catchment is home to an extraordinary diversity of wildlife:
- Platypus — confirmed at multiple sites along the main Tarwin stem
- Australasian Bittern — critically endangered; uses wetlands in the lower catchment
- Growling Grass Frog — endangered; found in farm dams and slow-flowing streams
- Broad-toothed Rat — uses dense tussock grassland in the upper catchment
- Regent Honeyeater — critically endangered; occasionally recorded in the Strzelecki Ranges